From: William James <w_a_x_man@...>
Date: 2007-10-20T10:05:03+09:00
Subject: Re: What's the ruby way of grouping elements of an array?

On Oct 19, 2:01 pm, Sam Kong <sam.s.k...@gmail.com> wrote:
> Hi,
>
> I thought this would be a common need but I couldn't find a method.
>
> Let's say I have an array of objects.
> I want to group the elements by a property of objects.
>
> people.group_by do |person|
>   person.age
> end
>
> The above method should return an array of arrays grouped by age.
>
> What's the ruby way for this case?
> I think I can implement it but I am sure that a good way already exists.
>
> Thanks.
>
> Sam


It's pretty simple.

class Array
  def group_by
    h = Hash.new{ [] }
    each{|x|
      h[ yield( x ) ] += [ x ]
    }
    h.values
  end
end

p %w(a little while ago I heard the tittering of a mouse).
  group_by{|s| s.size }